STCP 13 1 Issue 017 Invoicing and Payment

STCP 13-1 Invoicing & Payment Issue 017 – 01/04/2026 1 of 11 STCP13-1 Issue 017 Invoicing & Payment STC Procedure Document Authorisation Company Name of Party Representative Signature Date The Company National Grid Electricity Transmission plc SP Transmission Ltd Scottish Hydro-Electric Transmission Offshore Transmission Owner Competitively Appointed Transmission Owners STC Procedure Change Control History Issue 001 11/01/2005 First Issue Issue 002 04/03/2005 BETTA Go-Live version Issue 003 25/10/2005 Incorporating PA034 & PA037 Issue 004 31/01/2006 Incorporating PA045 Issue 005 18/11/2008 Incorporating PA052 Issue 006 19/10/2009 Incorporating PA055 and changes for Offshore regime Issue 007 20/11/2013 Incorporating PM069 Issue 008 01/04/2019 Incorporating changes for National Grid Legal Separation Issue 009 01/09/2020 Amendments to STCP13- 1 ‘Invoicing and Payment’ Clause 3.2 - Changes to TO Site Specific Charges Issue 010 29/10/2020 Annual Charge Setting - data submission flexibility Issue 011 01/07/2021 Issue 011 Issue 012 25/04/2023 Issue 012 incorporating use of ‘The Company’ definition as made in the STC PM0130 Issue 013 17/04/2025 Issue 013 Digital Communication System Integration PM0144 Issue 014 11/09/2025 Issue 014 CATO Go-Live version PM0134 STCP 13-1 Invoicing & Payment Issue 017 – 01/04/2026 2 of 11 Issue 015 26/11/2025 Issue 015 incorporating Competitively Appointed Transmission Owners to TO Lists on all Definitions – PM0151 Issue 016 12/02/2026 Issue 016 incorporating STCP Legal Text Rectifications January 2026 – PM0152 Issue 017 01/04/2026 Issue 017 incorporating Due Date for Monthly Payments to Transmission Owners (TOs) – PM0150 STCP 13-1 Invoicing & Payment Issue 017 – 01/04/2026 3 of 11 1 Introduction 1.1 Scope 1.1.1 This document defines the process associated with invoicing & payment activities between the TOs and The Company, as defined in the STC and meaning the licence holder with system operator responsibilities. 1.1.2 For the purposes of this document, the TOs are: • NGET; • SPT; • SHET; • All Offshore Transmission Licence holders as appointed by Ofgem; and • All Competitively Appointed Transmission Licence holders as appointed by Ofgem 1.1.3 For the purposes of this document, the Onshore Transmission Owners (Onshore TOs) are: • NGET • SPT • SHET • CATO STCP 13-1 Invoicing & Payment Issue 017 – 01/04/2026 4 of 11 1.2 Objectives 1.2.1 The objective of this procedure is to detail: • how the invoicing and payment process is addressed across The Company – TO interface; • how changes to charges (if applicable) are communicated and incorporated into invoices from the TO to The Company; • the requirements for exchange of information related to invoicing & payment activities; and • the lines of communication to be used. 1.3 Background 1.3.1 The Company shall be responsible for the calculation, development and invoicing of Connection and TNUoS charges. The TO shall be remunerated by The Company for the provision of connection and infrastructure assets and associated services. 1.3.2 The TO's revenue from The Company will be in three parts: • TO General System Charges as defined in Schedule Ten of the STC; • TO Site-Specific Charges as defined in Schedule Ten of the STC; and • Other Charges (ad-hoc activities) as defined in Schedule Ten of the STC. 1.3.3 The Company shall be remunerated by a TO for the following • The Company Charges in relation to Interruption Payments as defined in Schedule Ten of the STC; and • Other Charges (ad-hoc activities) as defined in Schedule Ten of the STC. 1.3.4 The majority of this revenue will be invoiced on a monthly basis (see sections 3.1 and 3.33), with the remainder on an ad-hoc basis (see section 3.66). 2 Key Definitions 2.1 For the purposes of STCP 13-1 Invoicing & Payment: 2.1.1 The Company Revenue Contact means the named contact within The Company for revenue issues as advised to the TOs from time to time. 2.1.2 Other Charges means those charges specified in Part Three of Schedule Ten of the STC. 2.1.3 TO General System Charges means those charges specified in Part One of Schedule Ten of the STC. 2.1.4 TO Revenue Contact means the named contact within the TO for revenue issues as advised to The Company and the other TO from time to time. 2.1.5 TO Site Specific Charges means those charges specified in Part Two of Schedule Ten of the STC. 2.1.6 The Company Charges means those charges specified in Schedule Ten of the STC. STCP 13-1 Invoicing & Payment Issue 017 – 01/04/2026 5 of 11 2.1.7 Financial Year Y means the current Financial Year beginning on 1st April and ending 31st March. 2.1.8 Net Transmission Network Revenue means revenue received by The Company via Transmission Network Use of System Charges in accordance with Section 14 of the CUSC. 2.1.9 TNUoS Charges, net of payments to The Company, the Authority, offshore transmission owner allowed revenue, electricity interconnector licensees, innovation funding winners, DNOs (Distribution Use of System charges for embedded OFTOs). means Transmission Network Use of System Charges in accordance with the CUSC. 3 Procedure 3.1 TO General System Charges and TO Site Specific Charges 3.1.1 The TO shall receive payment from The Company each month in the Financial Year for TO General System Charges. By the 5th Business Day of August each Financial Year the Company Revenue Contact shall contact via a Designated Information Exchange System the TO Revenue Contact requesting a forecast of their TO General System Charges for Financial Year Y+1 and for the five Financial Years from Financial Year Y+2 onwards. The TO Revenue Contact shall contact via a Designated Information Exchange System the Company Revenue Contact on or before 5th Business Day of October each Financial Year their forecast of the TO General System Charges for Financial Year Y+1 and for the five years from Financial Year Y+2 onwards. Revisions to the TO General System Charge can be made up to 7th January for Onshore TOs and 25th January for OFTOs each year for Financial Year Y+1 and for the five years from Financial Year Y+2 onwards. Should either day not be a Business Day then the deadline shall be the next Business Day. 3.1.2 The TO shall receive payment from The Company each month for TO Site-Specific Charges. On or before the 31st of October each year the TO Revenue Contact shall contact via a Designated Information Exchange System the Company Revenue Contact a schedule of the known monthly TO Site-Specific Charges per site per customer, for each month of the following Financial Year. TO Site-Specific Charges shall be broken down into components as defined in the TO licences. This schedule can be revised in accordance with clause 3.3.1 and 3.3.2. 3.1.3 When an OFTO licence is granted during the year, The Company Revenue Contact shall contact via a Designated Information Exchange System the OFTO revenue contact requesting a forecast of their TO General System Charges and TO Site Specific Charges for the current Financial Year and an estimate of the asset transfer date. The OFTO revenue contact shall share via a Designated Information Exchange System The Company Revenue Contact their forecast of their TO General System Charges and TO Site Specific Charges for the current Financial Year and an estimate of the asset transfer date. Revisions can be made to the TO General System Charges, TO Site Specific Charges and estimated date of asset transfer up to the date of asset transfer. On the working day following asset transfer a final revision is to be sent to The Company Revenue Contact. STCP 13-1 Invoicing & Payment Issue 017 – 01/04/2026 6 of 11 3.1.4 For CATOs, revisions can be made to the TO General System Charges and TO Site Specific Charges up to the close of the Post Preliminary Works Cost Assessment. On the working day following the close of the Post Preliminary Works Cost Assessment a final revision is to be sent to the NGESO Revenue Contact. When a CATO licence is granted during the year, the NGESO Revenue Contact shall email the CATO revenue contact requesting a forecast of their TO General System Charges and TO Site Specific Charges for the current Financial Year. The CATO revenue contact shall email the NGESO Revenue Contact their forecast of their TO General System Charges and TO Site Specific Charges for the current Financial Year. Revisions can be made to the TO General System Charges and TO Site Specific Charges up to the close of the Post Preliminary Works Cost Assessment. 3.1.5 For OFTOs or CATOs, the amounts forecast in 3.1.1, 3.1.2, 3.1.3 and 3.1.4 shall be accompanied by an invoicing schedule to detail the annual and monthly amounts for TO General System Charges and TO Site Specific Charges, and where appropriate, a breakdown of the latter charge into its components as defined in the TO Licences. 3.1.6 Each OFTO or CATO shall on the 1st Business Day of each month invoice The Company equal amounts over the remaining months of the year, matching the amounts provided under clause 3.1.2 or 3.1.3 and totalling the annual General System Charges and TO Site Specific Charges forecast in 3.1.1, 3.1.2, 3.1.3 and 3.1.4 less any one-off General System Charges that have been invoiced during the year. The Company shall pay the recurrent monthly OFTO or CATO invoice on the 2nd Business Day immediately following the 14th of the month. 3.1.7 The Company will pay the NGET, SPT and SHETL the Net Transmission Network Revenue which has been invoiced by The Company to Users (as defined in the CUSC) as Transmission Network Use of System Charges under the CUSC. For the avoidance of doubt payment is due by The Company to NGET, SPT and SHETL where the Transmission Network Use of System Charges have been invoiced even if not paid by Users (as defined in the CUSC) to The Company. 3.1.8 The monthly Onshore TO General System Charges payable to each Onshore TO will be calculated as follows: Financial Year Y year to date invoiced Net Transmission Network Revenue, less TO General System Charge payments already made by The Company to the relevant Onshore TO within the Financial Year Y. Any update of costs post the March invoice will be included through the Reconciliation processes defined in 3.2. 3.1.9 In the calculation of the monthly payment to Onshore TOs, payments to the Authority, interconnector licensees, innovation funding winners and The Company will be allocated on a flat monthly phased basis across the Financial Year. Payments to OFTOs, CATOs and DNOs (Distribution Use of System charges for embedded OFTOs) will be in accordance with existing payment schedule arrangements. 3.1.10 In respect of the Onshore TOs, for payments due from The Company for TO Charges forecast in 3.1.1 and 3.1.2, the following process shall apply: 3.1.10.1 On the 1st Business Day of each month, The Company shall confirm to the TO Revenue Contact the amount payable to the Onshore TO for the current month. 3.1.10.2 On the 4th Business Day of each month, the Onshore TO shall invoice The Company the monthly amount communicated to it under 3.1.9.1. 3.1.10.3 On the 2nd Business Day immediately following the 14th of each month The Company shall pay the Onshore TO the amount shown on the invoice issued to it by the Onshore TO in accordance with 3.1.9.2. STCP 13-1 Invoicing & Payment Issue 017 – 01/04/2026 7 of 11 3.2 Reconciliation Process 3.2.1 The Company and the Onshore TOs shall carry out and complete an annual reconciliation process in respect of charges made to Generators and Suppliers in accordance with the CUSC. 3.2.2 Generation reconciliation process: In accordance with the CUSC, The Company reconcile TNUoS Charges to Generators via the Generation reconciliation process. This will be reflected in the revenue payable to or by the Onshore TOs. On the 1st Business Day of May of each Financial Year, The Company will confirm the amount payable to or receivable from each Onshore TO to reconcile the Financial Year Y-1. On the 4th Business Day of May of each Financial Year Y, the Onshore TOs shall issue an invoice or credit note to The Company accordingly in relation to Financial Year Y-1. The Company or the Onshore TO as applicable shall issue payment by 30th May of Financial Year Y, or next available Business Day should the 30th not fall on a Business Day. 3.2.3 Initial Demand reconciliation process: In accordance with the CUSC, The Company reconcile TNUoS charges to Suppliers via the Initial Demand reconciliation process. This will be reflected in the revenue payable to or by the Onshore TOs. On the 1st Business Day of July of each Financial Year, The Company shall confirm the amount payable to or receivable from each Onshore TO to reconcile the Financial Year Y-1. On the 4th Business Day of July of each Financial Year Y, the Onshore TOs shall issue an invoice or credit note to The Company accordingly in relation to Financial Year Y-1. The Company or the Onshore TO as applicable shall issue payment by 30th July of Financial Year Y, or the next available Business Day should the 30th fall on a weekend. 3.2.4 Final Demand reconciliation process: In accordance with the CUSC, The Company reconcile TNUoS charges to Suppliers via the Final Demand reconciliation process. This will be reflected in the revenue payable to or by the Onshore TOs. By 31st October of each Financial Year, The Company shall confirm the amount payable to or receivable from each Onshore TO to reconcile the Financial Year Y-2. On the 4th Business Day of November of Financial Year Y, the Onshore TOs shall issue an invoice or credit note to The Company accordingly in relation to Financial Year Y-2. The Company or the Onshore TO as applicable shall issue payment by 30th November of Financial Year Y, or next available Business Day should the 30th fall on a weekend. 3.2.5 Invoices issued by TOs will be despatched via a Designated Information Exchange System agreed with The Company Revenue Contact. The TO’s bank account details shall be included with each monthly invoice. 3.2.6 All payments will be by BACS unless the value is above the relevant bank’s BACS payment threshold, in which case The Company will make a same day CHAPS payment instead. 3.2.7 In the Financial Year preceding the next regulatory price control period, The Company and the relevant Transmission Owners may notify one another and agree (on a unanimous basis only), any reasonable temporary adjustments to the provisions in 3.1 to allow them to be fulfilled. E.g. data substitutions, submission date changes. 3.3 Changes to TO Site Specific Charges STCP 13-1 Invoicing & Payment Issue 017 – 01/04/2026 8 of 11 3.3.1 Following completion of works detailed in contracts between the TO and The Company, it may be necessary to amend TO Site Specific Charges in line with the charges calculated from the Bilateral Agreements for any affected Connection Site. For those contracted changes, the charge change will be implemented to The Company in the first available monthly periodic invoice following completion of works, to incorporate charges from the appropriate date. 3.3.2 The TO Revenue Contact shall give no less than 1 month prior written notice to The Company Revenue Contact of any changes to the TO Site Specific Charges except where changes are in accordance with clause 3.3.1. 3.3.3 Ahead of any invoice being received by The Company, the TO shall provide The Company with a revised invoicing schedule confirming the changes being made to the TO Site Specific Charges. 3.3.4 The TO shall invoice The Company each month the amounts contained in the schedule, and The Company shall pay on the later of • the 15th day following the day that the TO’s invoice was despatched; and • the 16th day of the month to which the invoiced payments relate, unless, in such case, such payment day is not a Business Day in which case payment shall be made on the next Business Day. 3.3.5 Invoices will be despatched via a Designated Information Exchange System to The Company Revenue Contact. The TO’s bank account details shall be included with each monthly invoice. 3.4 Changes to TO General System Charges 3.4.1 Only under exceptional circumstances, can General System Charges be changed after final notification on 25th January or post asset transfer for the first year of existence of an OFTO, or for a CATO, following the Post Preliminary Works Cost Assessment. Exceptional circumstances means an event or circumstance that is beyond the reasonable control of the licensee and for which it should not reasonably bear the financial risk. 3.5 The Company charges 3.5.1 If an Affected User has exercised its rights pursuant to Section 5 (Events of Default, Deenergisation, and Disconnection), subsection 5.10 (Relevant Interruptions) of the CUSC, The Company shall notify the relevant TO as soon as possible. 3.5.2 The process for Event Reporting and Joint Investigation detailed in Section C, Part Three of the STC shall be started by either party (if not already underway as a notification of a Significant Incident) in order to reach an agreement that a Relevant Interruption has occurred. 3.5.3 Following agreement by all parties (the User, The Company and the TO), The Company will invoice the TO the relevant amount due to the Affected User. In the event of a dispute, “agreement” shall mean the determination following dispute proceedings as outlined in the STC. 3.5.4 The Interruption Payment shall be paid by the TO to The Company within thirty days of receipt of the invoice. STCP 13-1 Invoicing & Payment Issue 017 – 01/04/2026 9 of 11 3.6 Payment for Ad-Hoc activities 3.6.1 Where a payment is required between The Company and the TO that is not included in the monthly billing process, this shall be invoiced on an ad-hoc basis. The invoice shall reference a purchase order number where appropriate. 3.6.2 Where the payment is required by the TO this will be in accordance with Other Charges in Schedule 10 of the STC. 3.6.3 All invoices for payments for Other Charges in Schedule 10 of the STC shall be despatched not less than 30 days prior to the due date for payment. Payment shall be made by the recipient of the invoice within 30 days of the date of the despatch, or within 30 days of the invoice date, whichever is the later. 3.6.4 Paper invoices will be despatched by post and supported by a Designated Information Exchange System where feasible, to The Company or TO Revenue Contact, as appropriate. The bank account details of the Party receiving payment shall be included with each monthly invoice. 3.6.5 All payments will be by BACS unless the value is above the relevant bank’s BACS payment threshold, in which case The Company or the TO as appropriate will make a same day CHAPS payment instead. 3.7 Ancillary Payment Issues 3.7.1 All other payment related issues (e.g. addressing late payment by any party) shall be addressed in line with the STC. 3.8 Provision of Bank Details for Invoicing Purposes 3.8.1 Within 5 working days of section 8(A)3 notice being given to the OFTO, the prospective OFTO writes on company letter headed note paper to The Company revenue contact detailing bank details, trading name, trading address, invoicing address and invoicing contact. The letter to be signed by a company authorised signatory. STCP 13-1 Invoicing & Payment Issue 017 – 01/04/2026 10 of 11 Appendix A: Flow Diagram Note that the Process Diagrams shown in this Appendix A are for information only. In the event of any contradiction between the process represented in this Appendix and the process described elsewhere in this STCP, then the text elsewhere in this STCP shall prevail. S Charge Type TO The Company STCP13-1 Invoicing and Payment Monthly TO General System Charges Monthly TO Site-Specific Charges (SSCs) Calculate monthly payment due & inform TO Issue monthly invoice to The Company Pay monthly TO invoice Receive monthly payment Send invoicing schedule of monthly SSCs for FY+1 to ESO revenue contact. Issue updates during FY Y as appropriate Receive schedule/updated schedule Issue monthly invoice to The Company Pay monthly TO invoice Receive monthly payment STCP 13-1 Invoicing & Payment Issue 017 – 01/04/2026 11 of 11 External SO TO STCP 13-1 Invoicing & Payment Invoice SO containing ad hoc charge details, customer account etc Ad Hoc Check & Initiate Payment to TO Payment Received Invoice TO containing ad hoc charge details, customer account etc Check & Initiate Payment to SO Payment Received STCP 13-1 Invoicing & Payment Issue 017 – 01/04/2026 12 of 11 Appendix B: Abbreviations & Definitions Abbreviations BACS Banker’s Automated Clearance System CATO’s Competitively Appointed Transmission Owners CHAPS Clearing House Automated Payment System OFTO Offshore Transmission Owner SHET Scottish Hydro-Electric Transmission Limited SO System Operator SPT SP Transmission Limited STC SO-TO Code TNUoS Transmission Network Use of System TO Transmission Owner or Offshore Transmission Owner Definitions STC definitions used: Asset Transfer (OFTO Amended Standard Condition E12 - A1) Business Day CATO Connection The Company NGET Onshore Transmission Owner Other Charges (Schedule Ten) TO General System Charges (Schedule Ten) TO Site-Specific Charges (Schedule Ten)